What of Climate Change? Is there historical evidence for it?
Just recently, we have been involved in a considerable task of going through newspapers and other historical records to find evidence of climate change in East Anglia. There have certainly been changes. The sea froze off Southend at the turn of the 20th Century, and the Stour once froze so regularly as to allow an occasional skating race. However, these seem to be normal short-term variations within a fairly stable climate, so called 'mini ice-ages'. There have been warm periods before, including the one that ushered in Palladian architecture.
Ancient weather patterns in Britain are difficult to describe except in the most general terms. The best attempt at a historical analysis is probably that of H H Lamb (Climate Vol 2 Methuen 1977: 372-4, 384-5) who has suggested the following variations in the post-glacial European climate. Palaeometeorology and tree-ring analysis has filled in a lot of detail, but the broad analysis still seems valid:
- up to 6000 bc. Temperatures gradually rising with winters generally milder, and the summers rather warmer than today.
- 6000 to 3500 bc. A 'climatic optimum' with mild winters. The humidity was greater than before or after. The wind was generally westerly.
- 3500 to 1000/500 bc. A generally warm settled regime with some serious interruptions and fluctuations of temperature and humidity at c. 200 years intervals.
- 1000/500 bc to ad 100. A decisive shift to a colder, wetter climate in N. W. Europe, the most marked change being from c. 1000 to 700 bc, so that by the second half of the first millennium bc the weather would have been comparable with today. The winds in this period were generally N. W./N. in summer and W. in winter.
- ad 100 to ad 400. Some recovery of warmth and a tendency to be drier.
- AD 400 to ad 800. Reversion to colder, wetter weather.
- ad 800 to ad 1300 gradual improvement culminating in a warmer epoch in twelfth and thirteenth centuries.
- ad 1300 onwards. With some significant exceptions (e.g. the poor weather of the late fourteenth century, the 'little Ice Age' of the seventeenth century) and a cold period in late victorian times, the climate is thought to have been much the same as it is today.
The best that can be done in any investigation into weather effects in former times is probably to assume that, back to c. 1000 bc, the climate was generally as it is now, but with considerable variations that have lasted for up to a century.